Incanter - where is add-derived-column?

Question

The add-derived-column function seems ideal for what I want, which is to calculate the mean of values from several columns and add the mean to the dataset. 1st problem: I (use '(incanter core datasets ...)). But when I run this test: (add-derived-column :het [:a :b] (fn [:a :b] (+ :a :b)) data1) the repl says 'unable to resolve symbol: add-derived-column'. It is the same with the example given in the docs. The incanter docs indicate the function is part of 'core'. Has this function been moved to another package or am I doing something silly. Assuming this function is not lost 2nd problem (coming): for the vector of columns can I use this instead: (def colnames [:a :b :c ..]) (add-deriv... :newcol colnames (fn [colnames] (some calculation)) datavals)?